Solis was optioned to Triple-A Syracuse on Wednesday, Dan Kolko of MASN Sports reports.
Solis' demotion clears a spot in the bullpen for Brandon Kintzler, who was acquired from the Twins prior to Monday's trade deadline. While Solis had a chance to earn a high-leverage relief role when he was activated from the disabled list in early July, he squandered any opportunity of that happening by giving up runs in five of his six appearances over the past month. He'll aim to get back on track in Syracuse before likely rejoining the Nationals in September, if no injuries in the bullpen force an earlier promotion.